(1) Field of the Invention
The present invention relates generally to low resistance, high conductivity lead/acid batteries such as those particularly suited for the demands of aircraft battery applications, and which draw currents of 1000 amperes or more.
(2) Description of the Prior Art
The present invention is primarily intended for and will be described in conjunction with a lead-acid aircraft battery. Many aircraft batteries must meet rigorous military performance specifications. For example Military Specification MIL-B-8565J details the performance requirements for 24 volt, 30 ampere-hour batteries used for aircraft starting. These specifications require the batteries to output a specified voltage under a variety of loads and environmental conditions. The testing results in extremely high amperage drains on the batteries for extended periods of time. Known lead terminal connector assemblies have relatively high levels of electrical resistance because of their lead content and, thus, tend to heat up during the testing. In high power usage situations (greater than 1000 amperes.), the heat generated during the testing can cause the temperature of the battery terminal assemblies to rise approximately 350xc2x0 F. in a short period of time. Some Lead alloys have a melting temperature of approximately 350xc2x0 F. On warm days the heat load is sometimes sufficient to melt conventional lead alloy terminal connector components causing battery failures.
External terminals for the battery are generally molded into a rather large lead plug which includes an opening in one end thereof for receiving an electrode post. The terminal is connected to the post through the lead member by melting the lead of the post and the lug together.
Some types of batteries include a wall upstanding from the cover forms a well which surrounds the opening in the cover through which the electrode post extends. The lead casting is placed around the electrode post within the aforementioned well and the two lead pieces are welded or soldered together with the lead melting and generally filling the well. This lead casting gives a high electrical resistance between the terminal and the post. The instantaneous peak power or current carrying capability is therefore diminished from what the battery is theoretically capable of producing.
Further, the lead castings (2 for each battery) provide an additional 4 ounces of weight to the battery. This extra weight is important, particularly in aircraft batteries.
In my earlier application, Serial No 08/902669, filed Jul. 30, 1997, now U. S. Patent No. 6,001,506, I described a non-lead connector which provided light weight and creep resistance, the content of which is hereby incorporated by reference.
Thus, there remains a need for a new and improved terminal post assembly for low resistance, high conductivity, lead/acid batteries which has increased current carrying capacity. Further, the terminal post assembly should be capable of withstanding the heat load described above without any melting of the terminal components.
The present invention is directed to a low resistance high conductivity battery terminal particularly adapted for aircraft use. The term xe2x80x9clow resistance, high conductivity batteryxe2x80x9d as used herein is meant to include batteries that draw 1000 amperes or more.
This aspect of the invention is met by forming the connector of a conductive material having a non-lead content of greater than 50% and a melting temperature of greater than 450xc2x0 F. Such conductive materials include, by way of example, copper, brass, bronze, copper-nickel alloys, tellurium-copper alloys, beryllium-copper alloys, and similar materials. Materials such as copper exhibit a melting temperature in the range of 750xc2x0 F.
The connector may be formed entirely of the non-lead material, be formed by providing an insert of non-lead material imbedded in the lead connector, or be formed by use of a non-lead heat sink.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.